The present invention relates to the preparation of incorporated photographic amides. More particularly, the present invention relates to the preparation of incorporated photographic amides using a continuous process.
Amides are important functional groups in photographic couplers that are incorporated into photographic elements. Such couplers, known as incorporated photographic couplers, are highly water insoluble since they must not diffuse in the aqueous media used in the photographic element (T. H. James, Editor, xe2x80x9cThe Theory of the Photographic Process,xe2x80x9d Fourth Ed., Eastman Kodak, 1977, page 345).
Amides link the photographic dye-forming portion of the coupler to the parts of the molecule that control dye diffusion, hue, stability, and other photographically important properties. (T. H. James, supra). Amides also serve as important functional groups in incorporated photographic stabilizers that retard the degradation of the image dye that results from reaction of the photographic couplers with developing agents. See U.S. Pat. No. 5,561,037. Such amides are commonly known as, and are referred to in this application as, incorporated photographic amides.
In most cases, incorporated photographic amides are prepared by combining acid chlorides, or solutions of acid chlorides, and amines dissolved in organic solvent using a batch operation:
ArNH2+RCOCl+Basesxe2x86x92ArNHCOR+BaseH+Clxe2x88x92
In the batch process described in U.S. Pat. No. 2,801,171 to Fierke et al., water is excluded from the amide preparation process and an organic base such as pyridine is used to neutralize the acid released by the reaction. U.S. Pat. No. 5,041,605 to Huson et al. discloses that some incorporated photographic amides can be prepared in the presence of water, and European Publication No. 0608896A1 to Sumitomo Chemical Co., Ltd. teaches that water alone can be used as an acid-absorbing reagent. In all cases, the acid chloride is added slowly to a solution of the amine in the presence of the acid-absorbing reagent to create a reaction mixture.
Since acid chlorides react very quickly with water, the success of preparations of incorporated photographic amides in the presence of water is unexpected. The absence of complete destruction of the acid chloride by the water is due to the nature of the groups on both the amine and acid chloride. That is, incorporated photographic amides must contain substituents that increase their solubility in water-insoluble solvents. Consequently, both the amine and the acid chloride are highly insoluble in water, promoting the desired reaction in the organic phase, and limiting the undesired hydrolysis of the acid chloride.
In typical batch operations to prepare incorporated photographic amides, concentrations of the amine and acid chloride to be combined are not always precisely known since solvent-wet starting materials are sometimes used to prepare these reagents. This lack of control results in multiple test-and-adjust cycles for each batch of amide. Moreover, in batch operations a large vessel is needed to contain the entire contents of the reaction mixture. In addition, much of the total processing time in batch mode is used for activities not related to the reaction. In particular, much time is allocated to steps such as reactor purging, reactant and solvent loading, heating, cooling, washing processing solutions free of salts, filtering the product solution prior to crystallization, and crystallizing and discharging the product.
All of these factors lead to high manufacturing cost due to the inefficient processing afforded by batch operations. As such, it would be desirable to reduce manufacturing cost by minimizing inefficiencies, thereby resulting in faster overall processing.
The present invention relates to a method of making an incorporated photographic amide comprising a) continuously combining an amine capable of forming an incorporated photographic amide, an acid chloride compound, one or more acid-absorbing reagents, and one or more water-immiscible solvents to continuously form a reaction mixture; b) continuously reacting the amine and acid chloride to form an incorporated photographic amide; and c) separating the incorporated photographic amide from the reaction mixture.
In another embodiment, the present invention relates to a method of making an incorporated photographic amide comprising a) continuously combining a quantity of an amine, a quantity of an acid chloride compound, a quantity of one or more acid-absorbing reagents, and a quantity of one or more water-immiscible solvents to form a reaction mixture; b) controlling the pH of the reaction mixture from 4 to 8; c) continuously reacting the amine and acid chloride to form an incorporated photographic amide; and d) separating the incorporated photographic amide from the reaction mixture, wherein the steps b) and c) may occur in any order including simultaneously.
Advantages of the invention will be obvious from the description, or may be learned by practice of the invention. Additional advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory of preferred embodiments of the invention, and are not restrictive of the invention, as claimed.